MentorPi Workspace — Setup & Run

ROS 2 Jazzy | Ubuntu 24.04 | RA305 Robotics Programming

---

1. One-Time System Setup

Serial Port Access

The MentorPi communicates over USB serial via /dev/rrc. A udev rule creates this symlink automatically when the robot is plugged in.

Create the rule:

sudo nano /etc/udev/rules.d/99-rrc.rules

Add this line:

KERNEL=="ttyACM*", SUBSYSTEM=="tty", ATTRS{idVendor}=="1a86", ATTRS{idProduct}=="55d4", SYMLINK+="rrc", MODE="0666", GROUP="dialout"

Reload and apply:

sudo udevadm control --reload-rules
sudo udevadm trigger

Add your user to the dialout group (requires logout/login to take effect):

sudo usermod -a -G dialout pi

Verify the symlink exists after plugging in the robot:

ls -la /dev/rrc

Note: If you see Permission denied on /dev/rrc before the group change takes effect, run sudo chmod 666 /dev/ttyACM0 as a temporary fix.

---

2. Create the Workspace and Clone

mkdir -p ~/mentorpi_ws/src

cd ~/mentorpi_ws/src

Now clone the repository.

git clone https://github.com/KSU-Chad/rover_ws.git .

Note: The trailing . clones the repo contents directly into src/ rather than creating a nested subdirectory.

---

3. Environment Sourcing

The MentorPi requires a typerc environment file to be sourced before launching. This sets the machine type, lidar type, and other hardware variables that the driver nodes depend on. Without it, odom_publisher will crash on startup.

Source the following in every new terminal you open, in this order:

source ~/mentorpi_ws/src/.typerc
source ~/mentorpi_ws/install/setup.bash

---

4. Build the Workspace

cd ~/mentorpi_ws

colcon build --symlink-install

source ~/mentorpi_ws/install/setup.bash

Wait for the build to complete. Fix any errors before proceeding.

Note: --symlink-install links install files directly to source files, so changes to Python nodes and launch files take effect immediately without rebuilding.

---

5. Run the Rover — Three Terminal Windows

The robot motor controller must be plugged in to the RPi via USB before launching Terminal 1.

Terminal 1 — Launch the Robot

ros2 launch my_rover launch_robot.launch.py

This starts three things: the hardware driver (ros_robot_controller), the robot state publisher (TF tree), and the odometry publisher (motor commands + dead-reckoning odom). Leave this running.

---

Terminal 2 — Open RViz

rviz2 -d ~/mentorpi_ws/src/my_rover/rviz/view_bot.rviz

---

Terminal 3 — Teleop Keyboard Control

ros2 run teleop_twist_keyboard teleop_twist_keyboard --ros-args -r /cmd_vel:=/controller/cmd_vel

Click on Terminal 3 to make sure it has focus, then use the keyboard to drive the robot.

Note: The topic remap is required — odom_publisher listens on /controller/cmd_vel, not /cmd_vel.

---

Quick Reference

Terminal	Command
1	ros2 launch my_rover launch_robot.launch.py
2	rviz2 -d ~/mentorpi_ws/src/my_rover/rviz/view_bot.rviz
3	ros2 run teleop_twist_keyboard teleop_twist_keyboard --ros-args -r /cmd_vel:=/controller/cmd_vel

---

Known Gotchas

• Controller board must be plugged in before launching — /dev/rrc won't exist otherwise
• Source .typerc first — MACHINE_TYPE must be set or odom_publisher crashes
• Odometry is dead-reckoning only — odom_publisher estimates position from commanded velocity, not encoder feedback, so drift accumulates over time
• Vendor launch files use hardcoded paths — don't call odom_publisher.launch.py or robot_description.launch.py directly, they contain /home/localuser paths that will fail

---

Kansas State University Salina — Robotics and Autonomous Systems